Understanding Basic Architecture of a Disk(Solaris)

Introduction:

Before we start the administration parts of Solaris operating system it is must to know the basic architecture disk, Basically, a disk device has both physical component and logical components

The physical components have disk platters and read and write heads

The logical components have disk slices, cylinders, tracks and sectors

Structure of physical disk explanation:

1.The disk storage part is composed of a couple of platters

2.The platters rotate.

3.The head actuator arms move the read and write heads as a unit radially then the read and write heads read and write data on the magnetic surface on both the side of the platters.

Sector = Its a smallest addressable unit on a platter, by default one sector, can hold 512 bytes of data.It can be also known as disk blocks
Tracks = A series of sectors positioned end to end in a circular path.
cylinder=A bulk of tracks.

 

What are Disk Slices in Solaris?

We know after dividing the disk in to individual partitions we call it as a logical partition or LVM partition or raid based on the partition type we use in RHEL, In Solaris, we call it as a slice, once the disk is divided in to individual partitions it is known as disk slices.

For example, One slice can hold critical file system data and another slice on the same disk holds user related files and many more.

Note: A disk under the Solaris OS is divided in to 8 slices i.e labeled from slice 0 to slice 7

Note: Slice 2 it contains the important data about the whole disk, size of the disk, a total number of cylinders remains available for the storage of files and directories.

A starting cylinder and the ending cylinder define each slice.These  cylinder values say the size of a slice,

Let me show you one example

imagine I have total cylinder 3200 (in human readable format 32 GB)

slice 0 offset cylinder:(0-1500),so total cylinder value for slice 0 is 1501

slice 1 offset cylinder:(1501-2000),so total  499 cylinders

slice 2  offset cylinder:(0-3199),so entire   cylinder value is 3200

offset means starting cylinder

Let us have a look at the below tabular column about the disk slices

 

Disk slice Naming convention:

Knowing about the Disk slice naming convention is must in order to learn Solaris disk management an eight character string represent the entire name of the slice.These eight character strings include

1.controller number

2.target number

3.disk number

4.slice number

Controller number:

It identifies the Host Bus Adapter(HBA) which is responsible to control the communication between the system and disk unit. HBA is nothing but responsible for sending and receiving the commands and data to the device.

All controller numbers are assigned in sequential order such as c0,c1,c2,c3 so on…

Target Number:

Is nothing but it is a  unique hardware address that is assigned to each disk, tape, CDROM.Same as controller target numbers are assigned in sequential order such as t0,t1,t2,t3 and so on…

Disk Number:

This is the special number reflects the number of disks at the target location.The Disk Number is also called as LUN.

Slice number:

The slice number range starts from 0 to 7 i.e s0 to s7.Total eight slices

The below diagram shows the string that represents the full name of the disk slice.

In our next article, I will explain the OS device naming conventions in Solaris.

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About Author:

Hello readers! Let me introduce my self first. My name is Vasanth Nirmal Singh J S having 9+ years of experience in IT on all flavours of Unix operating systems ,Storage's and many more .. I would like to share my technical experience i have come across - can be help to other people. So in this blog, I'll post my thoughts related to ITIS. I'll share experiences that I've had while working in different environments. You can expect content related to Unix,Solaris,Linux,EMC Storeages,HP-UX and many others. I hope this blog can be useful for you! Your comments will be appreciated!

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